Magnetic pick-up for phonographs



Patented Sept. 30, 1930 Y PATENT OFFICE cmmco Y; CORONEL, or MANILA,rHrLIrPINE ISLANDS MAGNETIC PICK-UI FOR PHONOGRAPHS Application ledMarch 6,

This invention relates to magnetic pick ups for phonographs, the purposeof which is to translate the vibratory movements of a stylus, when actedupon by a phonograph record,

into 'electrical impulses and to utilize such impulses to actuatesuitable acoustic means for the purpose of reproducing in sound the un,

4d ulations or lateral deviations in the sound groove of t-he record.The advantages of devices of this character, over well known sound L boxreproduction embodying a diaphragm acting through a tone arm to a horn,are numerous-A and are generally' well known. Chieiiy among theseadvantages, however, is the fact that more satisfactory reproduction isobtained with almost any desired amplification and the mechanical noisesincident to the operation of .a diaphragm are wholly eliminated. YFurthermore, reproduction through malgnetic pick up apparatus is muchmore sensitive to movements of aa stylus than the diaphragm, and,accordingly, the sound grooves may be made much smaller and closertogether, so that the playing time of the record is materially increasedwhen magnetic pick up reproduction is employed.

Magnetic pick u s have heretofore been suggested and are nown generallyto the art, but these prior devices embody numerous disadvantages,certain of which it is the ob- Y ject of the present invention tominimize and other of which it is the objectof this invention toovercome.

The primary purpose of the invent n, therefore, is to provide a sturdy,durable evice which will cooperate with either hill and dale orlateralcut records. Attempts have been made to provide such devices inthe `fpast, but my experience with such' devices has shown that whilethey may operate with a fair degree of etliciency on either one or theother of these types of records, they will not operate with efficiencyon yboth types. Such 'devices invariably embody a single stylus adaptedtoserve in both instances, but when it is attempted to thus operate thedevice, it is found that it will operate with much greater efficiency onone type of record than on the'other type. So far as I am aware,

1929. Serial No. 344,624.

no' device of the char vcter under considera- Y cut type, both of thesemountings beingtconnected with an armature so that such armature. isresponsive tothe operation of either 3* of the styli. With the armatureis associated a suitable coil positioned between the poles of apermanent horseshoe magnet, the coil being stationary and thearmature'loosely placed therein and on independent rubber bushedbearings.

Suitable means is provided for maintaining the armature in neutralposition and this means is suiiiciently rigid to -hold the armature insuch neutral position notwithstanding the pressure of either stylus uponthe record, but nevertheless suiiiciently resilient to allow ofvibration of the armature by either stylus. The coil is included in acircuit which is adapted to be connected to the detector tube S0 0f aradio receiving set or to any other suitable electrical apparatus,whereby the pulsating current resulting in the coil from the vibrationsof the armature may be .amplified and acoustically reproduced with anydesired volume.`

` An important feature of the present invention resides in thesimplicity of the structure, the relatively .light weight of the movingparts 'which renders the device extremely1 90 sensitive and the compactassociation of suc devices into a relatively small housing; y

Another important feature of the invenJ tion resides in the fact thatal1 parts of the device are readily accessible and may be easily iremoved and replaced in the .event of damage or breakage incident torough-usuage.

' Features of the invention, other than those specified, will beapparent from the hereinafter description and claims, when read in,100

Vpractical embodiment of the invention,-but

the construction therein shown is to be understood as illustrative,only, and not as defining the limits of the invention.

Figure 1 is a plan view of the device with' the cover plate removed,

Figure 2 is a section on the line 2--2 of Figure 1.

. Figure 3 is Van end view of the device.

Figures 4 and 5 show one way of supporting the device for cooperationwith either lateral cut or hill and dale records.

Referring tothe drawings, l designates a permanent, horseshoe magnetprovided with pole pieces 2. The magnet and pole pieces are mounted upona suitable base plate 3 of non-magnetic material, such, for example, ascast aluminum by means of the bolts 4 having nuts 5. 6 designates abearing plate of nonmagnetic material, preferably brass, shown best inFigure 2 as bent intermediate its ends at substantially 90 degrees, sothat one arm of the plate overlies the pole pieces 2, while the otherextends between the legs of the magnet. This bearing plate is perforatedand the bolts 4 are threaded therethrough to firmly clamp the bearingplate 6 in position..

The arm of 'the plate which extends between.

the legs of the magnet is slotted as shown at 7 and through this slotextends a lever, the fulcrum of which is the pivot 8, which eX- tendsacross the slot. The lever is of the first class and has arms 9 and 10of unequal length, the arm 9 being the longer of the two andconstituting the armature of the magnet.

Positioned between the pole pieces of the magnet is a coil 26 which ismounted rigidly in position and through the center of the coil is formeda passage of sufficient size so that the armaturepi) may extend throughthe coil without touching the same and with sufficient clearance topermit vibration of the armature within the coil withoutcontacttherewith.

The free end of the armature 9 is secured in any suitable manner to thestylus bar 14. This stylus bar which is in the form of a lever ispivoted at 15 to one of the pole pieces in such manner as to beinsulated therefrom and the long arm 16 of this stylus bar is secured tothe armature while the shorter arm 17 is formed to constitute a holderfor a suitable stylus which may be secured in place by a thumb screw 18.The short arm' 10 of the armature lever is connected by means of asuitable link 19, preferably flexible, to a second stylus bar 20. Thislatter Stylus bar has arms of unequal length with the longer arm 21connected to the link 19, while the shorter arm constitutes a holder forthe stylus 22, shown in the drawings as a standard diamond point needle.

It is of course essential to the proper oparnese eration of the devicethat the armature 9 tend to remain in a substantially neutral posi tionwhich willno't be materially affected by pressure ofeither stylus upon arecord and in ordemto 4provide for; this, so-.called gap equalizers areemployed'. These gap equalizers are in the form'of rubber or otherresilient plates 23, shown best in Fig. 2. They are secured against thendsof the pole pieces by screws 24 passe 4through metallic washerplates 25. The screws and washer plates firmly hold the equalizers insuch position that theireontiguous ends will bear against the oppositesides of the armature 9 and normally tend to hold the armature in theneutral posi- .This coil is firmly secured in place in any suitablemanner, such, for example, as by clamping it between the plate 6 and thebase plate 3, and it will be noted from Fig.2 that the coil is providedwith a central opening through which the armature extends, this openingbeing sufficiently large so that the armature will not contact with thewalls of the opening irrespectivel of the degree of vibration impartedto the armature by either stylus. The wire leads from the coil 26 aredesignated 27. They are secured to suitable binding posts 28 supportedon a block of insulation material 29. This block 0f insulation materialis secured in place by a bolt 30 which has two nuts 31 and 32. The nut31 serves to clamp the block of insulation tightly to the base, whilethe nut 32 serves to secure one end of a cover 33 in position and also`functions to-tight-ly and rigidly attach the device to a suitablebracket 34. The part 34 is soldered to 35. In place of 34-35, aremovable bracket for attaching to the tone arm of the phonograph can bemadea part of the unit. The part 35 in practice constitutes any suitablesupporting element.

The cover 33 to which I have referred is of suitable non-magneticmaterial and is Vadapted to enclose all parts superimposed upon the baseplate, being held in position b v the nut 32 and also by the nuts 5 ofthe bolts 4. A suitable opening is provided in the cover plate throughwhich the stylus bar 14 is adapted to operate.

Wires 36 lead from `the binding posts 28 to any suitable amplifyingapparatus through any standard combined scratch filter and vol* umecontrol, such as a radio receiving set which serves to amplify thevariable current impulses and prepare them for reproduction by asuitable horn or other sound amplifying means. kThe relatively weakvariable electrical currents 4resulting -in the coil through thevibration of the armature 9 are thus sult-l ably amplified andtransformed into sound.

The device of the present invention Will be sensitive to all notes andWill perform with uniform reproduction with either lateral cut or hilland dale records.y The arrangement is convertible as stated for eithertype of record by merely turning, the unit and arm 90 degrees on anindependent set of pivot holes onthe arm or arm mounting, or by turningthe arm 35 on an especially j ointedl rod working loosely in a hole in asuitable weight.

In Figures 4 and 5, this structure is illustrated generally. 100designates a suitable weight adapted to rest upon the frame of thephonograph instrument and provided in its top with a socket into whichextends a rod 101 joined at 102 and carrying at its top a saddle 103 towhich the arm 35' is secured.

vWhen the parts are asshown in Fig. 4, the

ldevice is adaptedto operate upon hill and .dale records, but by'iieXing the joint 90 degrees, the parts will appear as shown in Fig.

5 to adapt the device to cooperate with lateral cut records. Figures 4and 5 `are illustrative of one of several Ways in which the part 35 bemounted to permit ofoperation of the device with the records of eithertype.

It can be used as a freely floating weight on the Edison phonographwhenan attachment to the Edison arm is incorporated, thusu'tilizing to thefull benet the Edison synchronized feed with all the attendantadvantages, and becoming interchangeable with any standard Edisonreproducer.

I wishv it understood, however, that the present device is not limitedto use on Edison phonographs, but it can be employed on any make ofmachine to play all ltypes of records.

The stylus bar for the lateral cut records is suitably supported toinsulatethe bar and minimize scratch and record Wear, While the gapequalizing members 23, preferably of soft rubber, can he renewedandadjusted Without dismantling the unit thereby preserving the strengthofthe magnet and assuring efficient operation at all times. As a matterof fact, all the parts are simple in 'mechanical construction, ruggedand easy Vto adjust and repair. The simple, light, one-V piece armaturehas relatively little inherentl inertia and permits the faith-fulreproductidn of all notes in the musical scale. The method shown is.only1 illustrative of one method.

VThe foregoing detailed description sets forth the invention in itspreferred, practical form, but the invention is 'to be understood asfully commensurate with the appended claims.

, Having thus fully described the invention,

what I claim as new and desire to secure by Letters Patent is v 1. In amagnetic pick-up for phonographs, a permanent horseshoe magnet, a coilpositioned between the poles of said magnet, a i

pivoted armature extending through the-coil, and two distinct andseparate stylus ba'rs mounted independently of the armat-ure and anddale and lateral cut records, both of Which stylus bars are separatelyand independently secured to the armature to render adapted torespectively cooperate with hill said armature responsive to thevibrations of either stylus bar.

2. In a magnetic pick-up for phonographs, a permanent horseshoe magnet,a coil positioned between the poles of 'said magnet, and

7 stationary'with respect thereto, a pivoted armature extending throughthe coil and movable4 with `respect thereto, and two distinct and'separate stylus bars adapted to respectively cooperate with hill anddale and lateral cut records, said stylus bars being respectivelysecured to the opposite ends of the armature to render saidarmaturerelponsive to v the vibrations of either stylus 3. In a magnetic pick-npfor phonographs, a permanent horseshoe magnet, a coil positionedbetweenthe poles of said magnet, a pivoted armature extending throughthe coil,

'and'two distinct and separate stylus bars adapted to respectivelycooperate with hill and dale. and lateral cut records, bothof whichstylus bars are secured to the armature brations of either" stylus bar,and .resilient gap equa'lizingm'eans to yieldabl counterbalance thenormal pressure on eit er stylus in 'order to maintain the armature inneutral position and permit of vibratory movement of the armaturetransmitted thereto from either stylus bar.

4. In a magnetic pick-up for phonographs,

a permanent horseshoe magnet a e011 positioned between the poles of saidmagnet, a pivoted armature extending through the coil,

and two distinct and separate stylus bars pivf oted for vibratorymovement in planes perpendicularto one another, said stylus bars ei'ngadapted for cooperation respectively with hill and dale and lateral cutrecords,

, .l 100 to render said armature responslve tol the v1 A end of thestylus bar connected to the free end of the armature, and a separate andindependent stylus bar positioned to vibrate in a plane perpendicular tothe irst mentioned stylus bar and operatively connected to the free endof the short arm of the lever, Whereby the armature is renderedresponsive to the vibrations of either stylus bar.

6. `In a magnetic pick-up for phonographs, lo a permanent horseshoemagnet provided with suitable pole pieces, a coil positioned between thepole pieces and ixedly .mounted with respect thereto, a first classleverhaving arms of unequal length supported on a iXedfulerum with the longerarm extending through n the coil in movable relation thereto andconstituting thearmature, resilient gap equalizing means for normallymaintaining the ar# mature in neutral position, a stylus bar mounted ona fixedV pivot with one end of the stylus bar connected to the free endof the armature, and a separate and independent stylus bar positionedto' vibrate in a plane, perpendicular to the first mentioned stylus barand operatively connected to the free'end of the short arm of the lever,whereby the armature is rendered responsive to the vibra tions of eitherstylus bar, each stylus bar coruprising a lever of the first class witharms of unequal length, the long arm being connected tothe armaturelever and the short arm constituting a stylus holder.

In testimony whereof I have signed the foregoing speciication.

CIRIACo Y. ooRoNEn

